Let's roll up our sleeves and solve this. We have 820 and we're going to multiply it by 159, essentially adding 820 to itself 159 times.
Step 1: 0 + 820 = 820
Step 2: 820 + 820 = 1640
Step 3: 1640 + 820 = 2460
Step 4: 2460 + 820 = 3280
Step 5: 3280 + 820 = 4100
Step 6: 4100 + 820 = 4920
Step 7: 4920 + 820 = 5740
Step 8: 5740 + 820 = 6560
Step 9: 6560 + 820 = 7380
Step 10: 7380 + 820 = 8200
Step 11: 8200 + 820 = 9020
Step 12: 9020 + 820 = 9840
Step 13: 9840 + 820 = 10660
Step 14: 10660 + 820 = 11480
Step 15: 11480 + 820 = 12300
Step 16: 12300 + 820 = 13120
Step 17: 13120 + 820 = 13940
Step 18: 13940 + 820 = 14760
Step 19: 14760 + 820 = 15580
Step 20: 15580 + 820 = 16400
Step 21: 16400 + 820 = 17220
Step 22: 17220 + 820 = 18040
Step 23: 18040 + 820 = 18860
Step 24: 18860 + 820 = 19680
Step 25: 19680 + 820 = 20500
Step 26: 20500 + 820 = 21320
Step 27: 21320 + 820 = 22140
Step 28: 22140 + 820 = 22960
Step 29: 22960 + 820 = 23780
Step 30: 23780 + 820 = 24600
Step 31: 24600 + 820 = 25420
Step 32: 25420 + 820 = 26240
Step 33: 26240 + 820 = 27060
Step 34: 27060 + 820 = 27880
Step 35: 27880 + 820 = 28700
Step 36: 28700 + 820 = 29520
Step 37: 29520 + 820 = 30340
Step 38: 30340 + 820 = 31160
Step 39: 31160 + 820 = 31980
Step 40: 31980 + 820 = 32800
Step 41: 32800 + 820 = 33620
Step 42: 33620 + 820 = 34440
Step 43: 34440 + 820 = 35260
Step 44: 35260 + 820 = 36080
Step 45: 36080 + 820 = 36900
Step 46: 36900 + 820 = 37720
Step 47: 37720 + 820 = 38540
Step 48: 38540 + 820 = 39360
Step 49: 39360 + 820 = 40180
Step 50: 40180 + 820 = 41000
Step 51: 41000 + 820 = 41820
Step 52: 41820 + 820 = 42640
Step 53: 42640 + 820 = 43460
Step 54: 43460 + 820 = 44280
Step 55: 44280 + 820 = 45100
Step 56: 45100 + 820 = 45920
Step 57: 45920 + 820 = 46740
Step 58: 46740 + 820 = 47560
Step 59: 47560 + 820 = 48380
Step 60: 48380 + 820 = 49200
Step 61: 49200 + 820 = 50020
Step 62: 50020 + 820 = 50840
Step 63: 50840 + 820 = 51660
Step 64: 51660 + 820 = 52480
Step 65: 52480 + 820 = 53300
Step 66: 53300 + 820 = 54120
Step 67: 54120 + 820 = 54940
Step 68: 54940 + 820 = 55760
Step 69: 55760 + 820 = 56580
Step 70: 56580 + 820 = 57400
Step 71: 57400 + 820 = 58220
Step 72: 58220 + 820 = 59040
Step 73: 59040 + 820 = 59860
Step 74: 59860 + 820 = 60680
Step 75: 60680 + 820 = 61500
Step 76: 61500 + 820 = 62320
Step 77: 62320 + 820 = 63140
Step 78: 63140 + 820 = 63960
Step 79: 63960 + 820 = 64780
Step 80: 64780 + 820 = 65600
Step 81: 65600 + 820 = 66420
Step 82: 66420 + 820 = 67240
Step 83: 67240 + 820 = 68060
Step 84: 68060 + 820 = 68880
Step 85: 68880 + 820 = 69700
Step 86: 69700 + 820 = 70520
Step 87: 70520 + 820 = 71340
Step 88: 71340 + 820 = 72160
Step 89: 72160 + 820 = 72980
Step 90: 72980 + 820 = 73800
Step 91: 73800 + 820 = 74620
Step 92: 74620 + 820 = 75440
Step 93: 75440 + 820 = 76260
Step 94: 76260 + 820 = 77080
Step 95: 77080 + 820 = 77900
Step 96: 77900 + 820 = 78720
Step 97: 78720 + 820 = 79540
Step 98: 79540 + 820 = 80360
Step 99: 80360 + 820 = 81180
Step 100: 81180 + 820 = 82000
Step 101: 82000 + 820 = 82820
Step 102: 82820 + 820 = 83640
Step 103: 83640 + 820 = 84460
Step 104: 84460 + 820 = 85280
Step 105: 85280 + 820 = 86100
Step 106: 86100 + 820 = 86920
Step 107: 86920 + 820 = 87740
Step 108: 87740 + 820 = 88560
Step 109: 88560 + 820 = 89380
Step 110: 89380 + 820 = 90200
Step 111: 90200 + 820 = 91020
Step 112: 91020 + 820 = 91840
Step 113: 91840 + 820 = 92660
Step 114: 92660 + 820 = 93480
Step 115: 93480 + 820 = 94300
Step 116: 94300 + 820 = 95120
Step 117: 95120 + 820 = 95940
Step 118: 95940 + 820 = 96760
Step 119: 96760 + 820 = 97580
Step 120: 97580 + 820 = 98400
Step 121: 98400 + 820 = 99220
Step 122: 99220 + 820 = 100040
Step 123: 100040 + 820 = 100860
Step 124: 100860 + 820 = 101680
Step 125: 101680 + 820 = 102500
Step 126: 102500 + 820 = 103320
Step 127: 103320 + 820 = 104140
Step 128: 104140 + 820 = 104960
Step 129: 104960 + 820 = 105780
Step 130: 105780 + 820 = 106600
Step 131: 106600 + 820 = 107420
Step 132: 107420 + 820 = 108240
Step 133: 108240 + 820 = 109060
Step 134: 109060 + 820 = 109880
Step 135: 109880 + 820 = 110700
Step 136: 110700 + 820 = 111520
Step 137: 111520 + 820 = 112340
Step 138: 112340 + 820 = 113160
Step 139: 113160 + 820 = 113980
Step 140: 113980 + 820 = 114800
Step 141: 114800 + 820 = 115620
Step 142: 115620 + 820 = 116440
Step 143: 116440 + 820 = 117260
Step 144: 117260 + 820 = 118080
Step 145: 118080 + 820 = 118900
Step 146: 118900 + 820 = 119720
Step 147: 119720 + 820 = 120540
Step 148: 120540 + 820 = 121360
Step 149: 121360 + 820 = 122180
Step 150: 122180 + 820 = 123000
Step 151: 123000 + 820 = 123820
Step 152: 123820 + 820 = 124640
Step 153: 124640 + 820 = 125460
Step 154: 125460 + 820 = 126280
Step 155: 126280 + 820 = 127100
Step 156: 127100 + 820 = 127920
Step 157: 127920 + 820 = 128740
Step 158: 128740 + 820 = 129560
Step 159: 129560 + 820 = 130380

So, 820*159 = 130380